my $str1 .= $self->sanitizeString($input1);
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will do the same thing as

my $str1 = $self->sanitizeString($input1);
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but it makes no sense to use the former.

The benchmarks show no difference in speed. (Anything under 1% is definitely meaningless. I question anything under 5%. I used kennethk's code, but changed timethese to cmpthese to produce more useful output, and changed the label to something meaningful.)

           Rate concat normal
concat 771935/s     --    -1%
normal 779433/s     1%     --
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